linux-kernel - Re: [PATCH v6 31/39] kasan, vmalloc: only tag normal vmalloc allocations

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Date:   Tue, 8 Mar 2022 16:48:02 +0100
From:   Vasily Gorbik <gor@...ux.ibm.com>
To:     Andrey Konovalov <andreyknvl@...il.com>
Cc:     andrey.konovalov@...ux.dev,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: Re: [PATCH v6 31/39] kasan, vmalloc: only tag normal vmalloc
 allocations

On Tue, Mar 08, 2022 at 04:30:46PM +0100, Andrey Konovalov wrote:
> On Tue, Mar 8, 2022 at 4:17 PM Vasily Gorbik <gor@...ux.ibm.com> wrote:
> >
> > On Mon, Jan 24, 2022 at 07:05:05PM +0100, andrey.konovalov@...ux.dev wrote:
> > > From: Andrey Konovalov <andreyknvl@...gle.com>
> > >
> > > The kernel can use to allocate executable memory. The only supported way
> > > to do that is via __vmalloc_node_range() with the executable bit set in
> > > the prot argument. (vmap() resets the bit via pgprot_nx()).
> > >
> > > Once tag-based KASAN modes start tagging vmalloc allocations, executing
> > > code from such allocations will lead to the PC register getting a tag,
> > > which is not tolerated by the kernel.
> > >
> > > Only tag the allocations for normal kernel pages.
> > >
> > > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> >
> > This breaks s390 and produce huge amount of false positives.
> > I haven't been testing linux-next with KASAN for while, now tried it with
> > next-20220308 and bisected false positives to this commit.
> >
> > Any idea what is going wrong here?
> 
> Could you try the attached fix?

Wow, that was quick!
Yes, it fixes the issue for s390, kasan tests pass as well.
Thank you!